A muscle produces maximal force when it's put into a stretched position against a load. So we're going to get those puppies into a loaded stretch and throw in some mechanical drop sets too.
Set the bench at a pretty low incline, somewhere between 30 and 45 degrees. For these, focus on getting the biceps into a fully lengthened position so that it's really stretched out with the palms facing forward at the bottom.
Choose a weight you can do for 10 reps, with 1-2 reps left in the tank, lowering the weight over 5 seconds on every rep.
From there, stand up and start doing alternating dumbbell curls, again taking 5 seconds to lower the weight. You can use a little bit of English here to get the weights moving but don't get too messy. Grind out as many reps as you can in this fashion without turning it into pure slop. Rest 2-3 minutes and then repeat.